These pumps, generally known as plunger pistons, have a head in which the ducts are formed and in which the intake and delivery valves are situated, a body separate from said head in which the actuation means of one or more pistons are situated, and means for fixing said pump body to the drive motor body.
More specifically, the drive shaft of the motor inserts into the pump body to lock torsionally to the hollow tang of the hub of a rotating inclined plate on the periphery of which the ends of the pistons slide.
In order to avoid friction, the ends of the pistons are rested on a rotating ring, with interposition of rollers, on the inclined plate.
The hollow tang of the hub is in turn supported by the pump body through a rolling ball bearing.
In known pumps the pump body is closed, on the motor side, by a shaped cover that carries the attachment arms to the body of the motor and acts as a seat for the bearing that supports the hollow tang of the hub of the inclined plate, as well as for an oil sealing gasket.
The cover is then connected to the pump body through peripheral bolts.
The known solution has a series of drawbacks that lie both in the constructive complication and in the difficulty of assembly of the pump.